The present invention relates to the field of photography and, in particular, to improvements in photographic apparatus of the self-developing type.
Photographic apparatus of the self-developing type are generally well known. Typically, these include a camera body having a film pack containing a stacked array of film units which are located adjacent a pair of pressure-applying rollers. The rollers are mounted adjacent a camera body exit slot through which an exposed film unit is advanced after being exposed. For advancing the film unit from the pack after exposure, there is provided a film pick arrangement which advances the topmost film unit of the film pack through a film pack exit slot. The film unit is brought into engagement with the rollers, and it is then further advanced by them while they simultaneously and progressively cause uniform spreading of the processing fluid in the film unit.
Earlier types of self-developing cameras were provided with a chamber for receiving at least a portion of the film unit as it was advanced from the rollers. The chambers served several purposes, one of which was to prevent further exposure of a treated film to ambient light. Use of these chambers, however, added to the overall dimensions of the camera. This was a disadvantage because it lessened the ability to devise an even more compact camera of the instant type.
Lately, there has been disclosed film units of the self-developing type which can be advanced into ambient light substantially immediately after the processing composition has been spread across at least a predetermined length of the film unit. Examples of such film units are described in commonly-assigned U.S. Pat. No. 3,415,644. With these film units at least a leading portion of the film unit can be advanced into ambient, while yet untreated portions can remain within the camera. By virtue of the ability to be advanced into ambient without the need for an exposure chamber it will be appreciated that compactness of the camera is enhanced.
The foregoing arrangement while serving satisfactorily, however, is nonetheless subject to potential drawbacks. One is the phenomenon generally referred to as lightpiping. More particularly, lightpiping arises when ambient light, which is actinic to the photosensitive layer in the film unit, is incident upon any portion of the transparent material exiting the camera during the film processing operation. Such ambient light is transferred down the transparent sheet and can extend past the processing rollers into the exposure chamber such that the unprocessed or untreated sections of the exposed photosensitive layer are struck by such radiation. This will result in the untreated sections fogging.
Several solutions for solving the problem of lightpiping have been put forth. One includes the use of an opacifying pigment in the light transparent layer itself. This solves the lightpiping problem without materially diminishing the quality of the finished photographic print. However, it should be recognized that it is also highly desirable to minimize light resistant characteristics of the film unit's transparent layer.
Another approach for overcoming the lightpiping problem is disclosed in commonly-assigned U.S. Pat. Nos. 3,940,774; 4,005,446; and 4,072,968. Essentially, these patents disclose the use of an opaque shade which covers the transparent layer of the film unit as the latter exits the camera. The shade is defined by a coil of opaque material mounted adjacent the camera exit in such a position and manner that the film unit's leading edge engages it and causes it to progressively uncoil while the film progressively exits the slot. The coil, as it uncoils, progressively covers portions of the film unit's light transmitting layer which have been treated with the processing composition. Hence, this prevents the ambient light which is actinic to the photosensitive layer from being reflected along the transparent layer to the untreated portions of the film unit. While the use of opaque shades of the type described above perform satisfactorily, there nonetheless exists the fact that such shades must be adequately stored adjacent the exit slot of the camera. Because of the coil's size and of the desire to protect its fragile physical strength from damage the camera housing must be made to accommodate it. By accommodating the opaque shade in such a manner the camera cannot be made as compact as possible. Moreover, such shades and their assembly into the camera add to overall manufacturing costs.